VITAL PRINCIPLE. $1 
ture approaching the boilmg point. The tendency of the 
fluids to fly off in vapour, becomes too great for the vital 
power to restrain. 
As the medium in which organized bodies live, is sub- 
ject to great variations of temperature, it is obvious, that 
unless Nature had provided some means of defence, many 
races would soon be extinguished, and others confined in 
their operations. But, in all the situations in which orga- 
nized bodies are placed, the means of protection against the 
vicissitudes of temperature are liberally provided. The 
locomotive faculty assists their escape from the scene of 
danger; and, where this is wanting, a covering of a body 
which conducts heat imperfectly, is bestowed to prevent 
the diminution of temperature, and various means are 
every where employed to check its pernicious increase. It 
is probable, that all organized beings, vegetable as well as 
animal, have an inherent power of generating cold or heat, 
according as circumstances require. Some curious experi- 
ments were performed. in illustration of this subject by 
Hunrex *. 
But the resources of organized bodies, employed to se- 
cure a suitable temperature, may be discovered in the 
circumstances of their physical distribution. Some are 
found subsisting under the influence of a vertical sun, 
while others survive the piercing colds of the arctic re- 
gions ; some prefer the sea-shore, others the summit of the 
mountains ; some live in the water, others on the dry land. 
To these different circumstances, there is an admirable 
adaptation of structure and disposition with respect to tem- 
perature ; so that no part of the earth or the waters can be 
considered as destitute of life. In these different stations, 
the different species can perform all the functions of exist- 

Sie. 
® Phil. Trans. 1726,-1778. aah 
